Signaling emergency braking by means of a brake light differently from other braking that is not emergency braking (normal braking) is known. Whereas, for normal braking, a brake light is, e.g., switched on continuously, when signaling emergency braking, e.g., pulsed control of the brake light takes place, which results in the brake light outputting a flashing signal. If the vehicle consists of a towing vehicle and a trailer vehicle coupled thereto, as is generally the case in the field of commercial vehicles, there is a need to signal the emergency braking visually not only on the towing vehicle but also on the trailer vehicle, because the trailer vehicle substantially conceals the brake lights of the towing vehicle from following vehicles. In this case, the brake light signal of the towing vehicle can present the emergency braking signal in the event of emergency braking, and the corresponding electrical operation of the brake lights of the towing vehicle can be electrically forwarded to the trailer vehicle, so that the emergency braking signal can also be presented using the brake lights of the trailer vehicle. As another possibility, the trailer vehicle itself can generate an emergency braking signal, e.g., if an electronic brake system installed in the trailer vehicle records unusually heavy braking using deceleration signals. In this case, signaling of emergency braking using brake lights of the trailer vehicle is also possible if the trailer vehicle is coupled to a towing vehicle that has no function for generating an emergency braking signal. This is, e.g., the case with older towing vehicles. However, a trailer vehicle improved in this way would not be compatible with a towing vehicle providing separate generation of an emergency braking signal.